1. Field of the Invention
The present invention relates to a feeder for feeding electronic chip components, and specifically to a feeder for feeding a plurality of randomly oriented electronic chip components in an aligned state.
2. Description of the Related Art
In order to feed electronic chip components such as capacitors, resistors, transistors, and filters, a plurality of randomly oriented electronic chip components are dispensed in an aligned state one by one using a feeder.
FIG. 7 illustrates a feeder 1 for feeding electronic chip components. This type of feeder is related to one aspect of the present invention.
The feeder 1 for feeding electronic chip components includes a hopper 3 for temporarily storing a plurality of randomly oriented electronic chip components 2. In the bottom of the hopper 3, a discharge opening 4 is formed. At the center of the discharge opening 4, a pipe 5 is formed in fixed fashion leaving a predetermined spacing between the pipe 5 and the inner periphery of the discharge opening 4. The fixed pipe 5 constitutes a portion of a conveying path 6 for leading (e.g., guiding) the electronic chip components 2 discharged from the discharge opening 4 in the aligned state. The inner diameter of the fixed pipe 5 is selected so as to be able to receive a chip component 2 only when a longitudinal direction of a chip component 2 agrees with the axial direction of the fixed pipe 5.
A movable pipe 7 is located between the inner periphery of the discharge opening 4 and the outer periphery of the fixed pipe 5. The movable pipe 7 surrounds the fixed pipe 5. The movable pipe 7 is driven so as to reciprocate in its axial direction as shown by a double-headed arrow 8. By the reciprocating movement of the movable pipe 7, electronic chip components 2 which are to be discharged from the discharge opening 4 are agitated such that electronic chip components 2 in the hopper 3 are smoothly moved and thereby led to the fixed pipe 5.
Among electronic chip components 2 in the hopper 3, only those which reach the top end of the fixed pipe 5 are received into the top opening of the fixed pipe 5, the received components 2 having orientations in a predetermined direction. The electronic chip components 2 in the fixed pipe 5 are guided in an aligned state. The conveying path 6, a portion of which is formed by the fixed pipe 5, is subsequently formed by a conveyer belt 10 circulating in the direction shown by an arrow 9. Therefore, the electronic chip components 2 discharged from the distal end of the fixed pipe 5 are subsequently conveyed by the conveyer belt 10 in the direction shown by arrow 9.
The electronic chip components 2 reaching the distal end of the conveying path 6 in this manner are picked up and held by a vacuum chuck 11, which constitutes a picking mechanism, so as to be mounted at a desired position on a wiring substrate, for example, by movement of the vacuum chuck 11.
In order to feed a plurality of kinds of electronic chip components 2 using the type of feeder 1 for electronic chip components described above, a plurality of feeding units 12 having hoppers 3 coupled to conveying paths 6 are disposed in parallel in the direction perpendicular to the plane of FIG. 7. The plurality of feeding units 12 are capable of reciprocating in unison in the direction shown by arrow 8. By the reciprocating movement, a feeding unit 12 feeds an electronic chip component 2 to the picking up position for the vacuum chuck 11.
The vacuum chuck 11 is controlled so as to reciprocate between two positions. At one end of the reciprocation, the electronic chip component 2 located at the distal end of the conveying path 6 of a specific feeding unit 12 is picked up, and then, at the other end of the reciprocation, this electronic chip component 2 is mounted at a desired position on a wiring substrate, for example.
In the feeder 1 for electronic chip-components formed as above, however, electronic chip components 2 in the hopper 3 undergo relatively intensive contact or collision, because of events like the following.
First, contact or collision of electronic chip components 2 can be attributed to the reciprocating movement of the movable pipe 7. That is, because of the reciprocating movement of the movable pipe 7, some electronic chip components 2 are in contact or collide with the movable pipe 7. Other electronic chip components 2 are in contact or collide with each other or with the inner surface of the hopper 3. This is caused by the agitation movement of the movable pipe 7. The greater the number of electronic chip components 2 in the hopper 3, the more shock caused by the contact or collision, which the electronic chip components 2 are affected by, because the weight of the electronic chip components 2 is cumulative in the bottom portion of the hopper 3.
Contact or collision of electronic chip components 2 can also be attributed to the starting and stopping of the movement of all the feeding units 12 in unison. That is, a feeding unit 12 is started and stopped every mounting operation, in general. The electronic chip components 2 accommodated in the hopper 3 repeat the contact or collision with each other or with the inner surface of the hopper 3 with each occurrence of starting and stopping. In order to increase the efficiency of the mounting process, the feeding unit 12 is rapidly moved and stopped under hard acceleration. This results in great shock to the electronic chip components 2 upon contact or collision as described above.
In order to smoothly guide electronic chip components in the hopper to the conveying path in an aligned state, the feeder for electronic chip components may be formed such that compressed air is jetted to electronic chip components in the hopper from outside (not shown), to agitate electronic chip components. In this case, electronic chip components also undergo contact or collision upon agitation.
Furthermore, in order to continue the mounting operation for a long time by reducing the frequency in which electronic chip components 2 are replenished in the hopper 3, each hopper 3 must accommodate a substantial number of electronic chip components 2. Therefore, among electronic chip components 2 in the hopper 3, there are chip components supplied to the mounting process after a relatively short stay in the hopper 3, while there are chip components that remain in the hopper 3 for a relatively long time. The electronic chip components 2 that remain for a long time in the hopper 3 undergo contact or collision many times resulting in potential quality deterioration. That is, there may be mechanical failure of electronic chip components 2 or degradation in solderability of outer electrodes of these chip components 2. When an electronic chip component 2 with deteriorated quality is mounted on a wiring substrate, the electronic chip component 2 is required to be replaced after mounting, thereby reducing productivity.